M IND O VER M ATTER Explain p.73-79

E NTRY T ASK Begin a new header/thread in your notebook “Mind over matter” Write the Learning Target: I can explain that the densities of various substances are related to differences in the particles that make them up. Skills: I can calculate density given mass and volume. I can use a substance’s density and volume to calculate mass. Update your Table of Contents

E NTRY T ASK

M IND OVER M ATTER Read the Introduction p. 73 Read “Density” p & Take Notes. Be able to define: Density The relationship between 1 mL and 1 cubic centimeter (cm 3 ) The units normally used to report density Physical Property Intensive Property Extensive Property

M IND OVER M ATTER Density is the ratio of a material's mass to the volume it occupies. g/mL or g/cm 3 g/mL is the same as g/cm 3 because a 1g cube that is 1cm on each side will displace Exactly 1mL of water This ratio is constant for a given substance, for constant temperature and pressure. This means that the density is the same regardless of the sample size of your substance (if pressure and temperature don't change)

M IND OVER M ATTER Example: 3 rings have the following densities: silver ring density = 10.5 g/cm 3 gold ring density = 19.3 g/cm 3 platinum ring density = 21.1 g/cm 3 If each ring has a mass of 6 grams, how do they compare in size (smallest to largest)?

M IND OVER M ATTER If each ring has a mass of 6 grams, how do they compare in size (smallest to largest)? In order of their densities: silver ring density = 10.5 g/cm 3 (lowest) gold ring density = 19.3 g/cm 3 platinum ring density = 21.1 g/cm 3 (highest) If all 3 rings have the same mass, then the volume (size) must be different: As the density increases, the volume decreases. Platinum (smallest); Gold; Silver (largest)

M IND OVER M ATTER Macroscopic View: We can see density differences: by observing how substances behave together a candle floats in isopropyl alcohol a candle sinks in water oil floats on water the candle acts differently because each liquid has a different density.

M IND OVER M ATTER Macroscopic View: We can see density differences: on a graph of mass vs. volume steeper slope = higher density

M IND OVER M ATTER Physical Property - a property of a material or substance that can be observed or determined without changing the identity of the material. Intensive Property - a property whose value is independent of the amount of material tested. Examples: temperature, pressure, viscosity, density, melting point, boiling point Extensive Property - a property whose value depends on the size or amount of material tested Examples: mass, volume, length, heat, energy, electrical resistance

M IND OVER M ATTER Answer P&P #2a,b,c pg. 75/76 in your notebook! Show all your work.

A N I NTERVIEW WITH D EMOCRITUS Ancient Greek Science roleplay Read pg Be able to define and explain the following: Atom Element Compound Molecule Pure substance Mixture

A N I NTERVIEW WITH D EMOCRITUS Democritus was a greek philosopher and scientist from 400 BC. Didn't have fancy equipment and tools to run tests and experiments Relied on "thought experiments" - using imagination to logically reason through a problem Democritus thought about what it would mean if he took a gold cube and kept cutting it in half into smaller and smaller pieces. the density and characteristic properties of each smaller piece would remain the same because they were still pieces of gold

A N I NTERVIEW WITH D EMOCRITUS at some point he would reach the smallest piece that would still retain the characteristics of gold. The smallest piece was called "atomos" (cannot be further divided) Atom = fundamental unit of matter

A N I NTERVIEW WITH D EMOCRITUS element - a substance composed of atoms having an identical number of protons in each nucleus. An element cannot be reduced to simpler substances by normal chemical means. atom - the smallest unit of an element/ the fundamental unit of matter compound - a substance formed by the combination of atoms of one or more elements

A N I NTERVIEW WITH D EMOCRITUS molecule - an electrically neutral group of two or more elements held together by chemical bonds. pure substance - a substance that can be divided down to a single atom or a single molecule. Pure substances always have the same characteristic properties. mixture - physical combinations of substances. Mixtures may have some of the same properties of the constituent substances, but often have new properties.

R EFLECT & C ONNECT Complete R&C #1-3 p. 79

R EFLECT & C ONNECT #1 Question: According to the ideas of Democritus, what might account for 1cm 3 of one substance being heavier than 1cm 3 of another substance? Democritus said that all matter was made up of tiny particles called atoms. He believed that the atoms that made up one substance were different from the atoms that made up another substance. He also believed that if one substance had a greater density, then that atoms that make up that substance must have a greater mass than those that make up the other substance.

R EFLECT & C ONNECT #1 Do you think that's the whole story? Diamonds and graphite are both made of atoms of carbon, yet they have different densities. Can you think of some reasons why?

R EFLECT & C ONNECT #1

R EFLECT & C ONNECT #2 2. The densities of most woods are reported as a range of values. The densities of most pure metals, such as silver and platinum, are reported as a single value. Why? Trees are alive and grow. Metals are not! Trees soak up water and their growth varies from year to year, so their densities are not a "set" value.

R EFLECT & C ONNECT #3 3. Ice floats in water, but sinks in rubbing alcohol. Draw sketches representing these observations at the microscopic level